Switch import's behaviour to absolute imports for json module
Switch import's behaviour to absolute imports for json module

Downstream [1], when packaging cloudkitty, we hit the issue of
json module importing itself, instead of standard library's
version.
This switch fixes the issue.

[1] https://review.rdoproject.org/r/#/c/23860/

Change-Id: If9aca985ebc04cc155d30aa49302413005a7ce97

openstack/cloudkitty,openstack/cloudkitty